Telephone-exchange system



Feb. 9 1926'.

1,572,679 A. C. POWELL TELEPHONE EXCHANGE SYSTEM Filed Nov. 23, 1923 5 sheets-sheet 1 Een. 9 192s, y

A. C3. POWELL TELEPHONE EXCHANGE SYSTEM 5 sheets-shee't 2 Filed NOV. 25, 1923 Feb. 9 192s.

-A c. Pom/ELL TELEPHONE EXHANGESYSTEM l Filed Nov 25, 1925 ySheets-Sheet 3 Feb. 9 1926.

A. C. POWELL TELEPHONE EXCHANGE SYSTEM Feb. 9 192s. .1,572,679

A. C. POWELL TELEPHONE EXCHANGE SYSTEM med Nov. 23, 192s 5 snetS-sheet 5 Patented Feb. 9, 1926.

anatra UNITED Slltl FATlilhlll FME.

ALBERT C. POVELL, OF NEW YORK, N. Y., ASSEGNGR TO WESTERN ELECTRIC COM- PANY, NCORPOBATED, OF NEVI YORK, N. Y., A CORPORATION OF NEW YORK.

TELEPHONE-EXCHANGE Application lcd November 23, 1523.

To au atv/om t may concern.'

Be it known that I, ALBERT C. Pownni., a citizen of the United States of America, residing at N ew York city, in the county of Bronx, State of New York, have invented certain new and useful Improvements in TelephoneExchange Systems, of which the following is a full, clear, concise, and exact description. Y

This invention relates to a telephone exchange system for use between mechanical and manual offices.

The object of this invention is an improved means to connect an).7 line in a full mechanical step-by-step central oiiicc to any desired line in a distant manual central iiice.

ln accordance with this invention trunk circuits incoming from the full mechanical step-by-step central oliice are provided at the manual central ciiice, any one of which may be reached from any line in the full mechanical step-by-step central office by removing the receiver at the station associated with said line and dialing a predetermined digit or combination of digits known as the otlice code. The trunk circuit in turn extends the connection to a pre-selected common circuit sometimes known as a recorder and register circuit,

and all further selecting signals are recorded in the recorder and register circuit. After all the selecting signals required arereceived the register circuit proceeds in combination with an indicating` device to display the number of the desired called line before an operator in the manual central oiiice, who, thereupon. completes a connection to the called line. Signaling follows automatically and when the called party answers, the talking circuit is automatically established.

A feature of this invention is an improved arrangement whereby a time interval is measured olf by the recording` device to delay the progress of the call long enough to permit the calling line to dial a party code if required. but permitting the call to proceed immediately after the party code is dialed, or in any event, after the predetermined time interval elapse's.

Another feature of this invention is an arrangement providing` the operator with a signal in case the complete code of a called number is not dialed together with means Serial No. 676,478.

for discharging the recorder, and rendering it available immediately for other calling lines which may be in waitino.

Another feature of this invention is an arrangement hereinafter referred to as the steering relay device whereby the various register switches are connected in proper sequence to the impulse circuit controlled by the calling station.

Another feature of this invention isy the lighting of a lamp before the operator should the calling subscriber fail to replace the receiver on the switchhook after a pre" determined time interval has elapsed.

@ther features will appear from the detailed description.

Fig. l shows a circuit arrangement for providing a disconnect signal to the operator after a suitable delay, when only the called party replaces the receiver upon the substation switchhook after conversation is completed.

Fig. EZ in its upper' left-hand corner shows a calling subscribers station in a full mechanical step-by-step machine switching svsteni; the usual primary and secondary line switches PLS and SLS. a first or oiiice selector S, and a repeater R, all located in the mechanical central office CO; the balance of Fig. 2 and a portion of Fig. 4 show 85 the equipment and circuit arrangement required for the trunk circuit which originates iu the full mechanical central office CO (Fig. 2) and terminates in a plug and cord in the manual central oflice MCO (Fig. 4). 90 ln the upper right-hand corner of Fig. 4 is shown a called subscribers station in the manual central oiiice MCO, accessiblev to the trunk circuit shown in Figs. 2 and 4. In the lower lett-hand corner of Fig. 2 is shown 95 the recorder finder switch having access to the recorder circuit (Fig. 3) and the numerical register switches (Fig. 5). The numerical switches shown in Fig. 5 each have three banks associated with indicatino; lamps, the horizontal row of banks to which brushes 501. 561, etc. have access being for the home position, the top horizontal row being for the adjacent left position, and the horizontal row to which brushes 502, etc. have access being for the adjacent right position. The banks of these three horizontal rows have lamps connected to each terminal thereof for indicating the desired number. For simplification of the 110 switches must now be stepped to the terminals associated with the next idle recorder` circuit. This is accomplished as follows: There is a relay T (Fig. 2) individual to each trunk circuit and whenever any trunk circuit is not in use, the corresponding` relay TR-2 connects battery at the contact corresponding to 218 through the winding ot its T relay to the lead 230, which is common to the multiple arcs of all the recorder finder switches, by way ot' all the parallel circuits correspendingl to 218, winding' ot relay T, 240 and brush Assuming that the brush of one or more other recorder finder switches corresponding' to the brush 220 is resting upon the terminal correspondii'ig to terminal 250 ot the recorder inder switch multiple bank, parallel circuits through all the relays T will be connected by way ol common lead 230, terminal 250, brush 220 to ground at contact 2410 ot' the relay @1 2 (Fig. 2). The various relays T will operate and close obvious local circuits to operate the various associated stepper magnet-s similar to 210 (Fig. 2), and in releasing will step their recorder iinder switch brushes terminals of the next recorder circuit group. Whenever the recorder und i brushes come to rest upon the test ter.,- of an idle recorder circuit the ground to hold the relays T operated, will be opened and these relays will release, prcyenting the associated stepping niagnets from rotating` the switch brushes any further until the seizure of another trunk circuit necesitates a recurrence ot this cycle of operations.

The operation ot relays Cl-l and C122 extend the leads 231, 233, 234e, and 235 hy way of brushes 221, 223, 224; and 225 tor purposes which will hereinafter be nia/de apparent.

It has been observed that the recorder' circuit (F ig. 3) is made busy (ground at 210 when the relay Cil-2 operates. This immediate busy condition is intended to refent the possibility of a double seizure ot a recorder between the time the brushes come to rest upon the terminal group of a particular recorder, and the time required to operate relay GRD (Fig. 3), which supplies at the ground intended to malte the recorder circuit test busy to all other recorder iinder switches, (except the one in Fig. 2 to which it is connected) until the recorder circuit has completed all its functions as hereinafter described.

L ii., t0 mirc in the Dialing.

circuit including the-,repeater R and the relay A.. Relay A which is a fast relay, is designed to follow the impulses reproduced by the repeater R. The impulsing circuit to operate the stepper switch 515 (Fig. 5) which responds to the first numerical or thousands digit of the dialed number, is as follows: ground, armature 229 ot' relay A, 236, 237, 238, 239, 216, 411-6, 1147, L148, 1419, 257, 241, brush 221, 231, 331, 304, 305, 306, 307, 308, 309, 310, 311, 312, 513, 514, 515, 516, 517,v 318, winding oit relay ADV to battery at 310. The relay B (Fig. 3) is conneet-ed at 313 to the lead 305 which results in the relay l being in parallel with the step per 515.

Relay B also operates and closes an auX- iliary or booster circuit to insure the proper operation of the stepper 515 as follows: Cirroui'ul, arnriture 320 of relay HLD, 321, 323, 325, 326, 327, 328, 532, 515,

.l-18, winding ot relay ADV to battery at 319. The stepper 515 and relay ADV operate in series. Stepper 515, in operating, opens its operating circuit at its armature If el, but the stepper does not release because booster circuit is still closed at relay ll. l'rlhen the impulse. relay A re-operates, relay l releases, opening the booster circuit through stepper 515 which now releases and, on its baclnyard strolre, rotates the brushes 500 to 505, inclusive, one step in a counter clockwise direction to the terminal 506 and the corresponding terminals oit the` other arcs oit the saine switch. lilith brush 505 resting' upon terminal 506 a circuit is closed through the relay STA (Fig. 3) as follows: ground, armature 320, relay HLD (Fig. 3) 321, 314, 315, 316, 317, winding' of relay ST-l, 320, 336, 536, 505, 506, 537, 337, 338 to battery at 339. Relay ST-l will not operate at this time as it is shunted by a path through the low r sistanee 340y to ground at armature 341 of relay ADV.

Relay l il and stepper 515 follow the iml pulses produced by the impulse relay A (Fig. 2) and relays SLO Fig. and ADV (Fig. 3) which are slow to release, remain operated throughout the thousands .impulse train. The stepper 515 rotates one sten impulse until the train ot impulses produced by relay A. cease.

After the last impulse or" the thousands diog't train of impulses ceases, relay ADV (Fig. releases, remoti; r at 341 the low `resistance shunt 3-/10 trom around the relay Still which now operates and loclis in an obvious local circuit. iVith the relay ST4. operated, :he impulsing and bois circuit-.s are transferred at .its ari?. 311 and 32?, respectively, 'from the stepper ot the thousands re te' sw'tch, to the stepper 525 associated with the `huiiulrewls rea'- ister switch. l

The digit correspondin5l to the hundreds per y llO digit of the desired number is now dialed at station 20() and the stepper 525 operates and rotates the hundreds register switch which takes the proper setting in the same general manner as the thousands reg'ster switch. At the end of the impulse train, relay ST-2 operates and locks in the saine general manner as relay SST-1, and transfers the impulsing and booster circuits at its armatures 310 and respectively to the stepper' 535 of the tens digit register switch.

ln lilre manner the tens digit is'registcred and relay ST-3 operates and locks and transfers the impulsing and booster circuits at its armatures 309 and 325 respectively to the stepper 545 of the units register switch. After units registration is completed, relay ST4; operates to transfer the impulsing and booster circuits at its armatures 307 and 324C, respectively, to the stepper of the stations register switch.

lt is necessary to delay the dsplaying of the called number on the indicating device until the calling party at station 200 has had sufiilcient time to dial the party code of the called station where a party code is required, and this is accomplished by using a display delay device in the manner hereinafter described. The relay SST-el, which operated after units registra-tion was completed, connects the interrupter 3%1-2 to the relay BB by way of 3&3 and 34d, and the relay BB operates and releases under ycontrol of the interruptor 342. Each time relay BB operates ground is connected to lead 345.

pulse is connected to lead by relay BB, the relay 7 operates as follows: battery,

'left winding relay Z, winding relay 7, 346,

to ground at The relay which is in series with tbe relay 7 is marginal and will not operate under this circuit condition. The operation of relay 7 connects ground by way of 3&9, 350 and 351 to the right winding of relay Z which is thereby connected in series with its left winding and the winding of relay 7. No change is effected in the circuit., however, due to the short-circuiting of the right winding of relay Z by the ground at relay BB by way of 346 and 3115.

Second Stage-Uien relay BB releases removing ground from lead 345, relay Z operates as follows: battery, left winding of relay Z, winding relay 7, right winding relay Z, 349, 350 to ground at 351.

Third Steger-Uien relay BB reoperates the relay 7 is short-circuited by ground on lead 34:5, causing the relay to release, but relay Z holds to the same ground by way of 347 and 3&5. The relay W1 now operates as follows: battery, left winding relay Z1, winding relay 71, 352, 354., 3&3, 350, to ground at 351. Relay Z1 is so designed that it will not opera-te under this circuit condition.

Fourth stage.-7hen relay BB releases removing ground from lead 345, the holding circuit through the left winding of relay Z is opened and relay Z releases,removing the short circuit from the right winding of relay Zl, which operates over the following circuit: battery, left winding relay Z1,

winding relay 71, right winding relay Z1, 355, 350, to ground at 351.

These four stages constitute a complete cycle of operations of the relays Z1 and 7. lt is evident that relays Z1 and 71 will remain operated over the circuit last described, until. solid ground is again connected to 353, by way of 354 and 3113. This cannot occur' until the third stage of the cycle is again reached when relay Z will be operated and relay 7 released, releasing relay 71 and operating relay 72.

During the fourth stage of the second cycle, relay Z2 operates and locks to ground in series with relay 72. telay Z2, however, will not `release during subsequent Ichanges in the condition of any of other tive relays in the combination. rIbis is because when relay 72 is operated, relays Z2 and 72 lock in series by way of 356 and 357 to ground at 350, and when relay 72 is normal, relay Z2 is locked over the circuit by way of 358, 359, 391 and 350, to ground at 351.

vThe relay BB continues to function under control of interrupter 342, and the Z, 7, Z1, 71 and 72 relays will continue to opera-te and release in accordance with the following table: (It will be remembered that during the fourth stage of the second cycle, relays 72 and Z2 are operated.)

Thz'rd cyclo.

F rrst stage-Relay 7 operates; relays 72 and Z2 hold.

Second stage-Relay Z operates; 7. 72 and Z2 hold.

Third stage- Relay 7 releases; relay 71 operates; relay Z, 72 and Z2 hold.

F ourth stage- Relay Z releases; relay Z1 operates; rela-ys 71, 72 and Z2 hold.

Fourth cycle.

relays F rst stage-Relay 7 operates; relays 71, Z1, 72 and Z2 hold.

VSecond stage-Relay Z operates; relays 7, 71, Z1, 72, and Z2 hold.

Third stage-Relays 7, 71 and 72 release; relays Z, Z1 and Z2 hold.

F oarth stage-Relays Z and Z1 release; relay Z2 holds.

F irststage-Belay 7 operates; relay Z2 holds.

Third stef,:go.--Relays )2V and W1 release;

relays Z, Z1 and Z2 hold.

It is thus evident that during the third stage of the sixth cycle, the saine relays (Z, Z1 and Z2) are operated duringl the third stage of the fourth cycle.

As long` as relay Z2 is locked by Way of 350 to ground at 351, the relays will repeat the operations from the third stage of the fourth cycle to the third stage of the sixth cycle. Hence, the maximum number of combinations obtainable is represented by the t table from the first stage of the first cycle to the second stage of the sixth cycle, or a total of twenty-two stages.

lf we regard each malte and break of interrupter 342 (or two of the stages) as one unit, We'have a total of eleven units in which We may delay the further advance of the call after units registration, in order to allow the calling station 200 to dial the station code, if required.

lf the interrupter has a make period of .5 seconds, and a break period of .5 seeonds, the delay interval Will be a` maximum o-l veleven seconds. 1f the interrupter 342 has a makeperiod of .3 seconds and al break period of .2 seconds, the delay interval will be a maximum of live and one-half seconds.

Any other desired delay may be obtained by varying` the number of impulses per second produced by interrupter 342, by insert ing additional Z and 1V relays in the circuit, or by changing the WiringI of leads 360 and 361 at the contacts of the relays Z and 1.7, etc.4

Let us assume that leads 360 and 361 are closed When relays Z1 and Z2 are operated, as shown by the Wiring in Fig'. 3, then the leads 360 and 361 Will be connected together in the fourth stage of the third cycle or after an interval of six units, and assuming` interruptor 342 has .3 seconds make and .2 seconds break, the delay after units registration Wi-ll be a maximum of three seconds, which ordinarily affords ample time to the calling; station to dial the station code, Where required,

No stations pulses.

Assuming stations pulses are not required,

the LP relay (Fig. 3) Will opera-te after the relays proper delay as follows battery, Winding reuy Lr, ses, seo, ses, ser, ses, ses, ser, 507,V

Stations pulses.

Assuming, however', that stations pulses are required, then stepper 555. will be energized over the iinpulsinp circuit previously traced by Way of 307 and 324 of relay SlT-4 (Fig. 3). rlhe stepper 555 Will set the register brushes 590 to A595, inclusive, in aiccordance With the number of impulses received over the impulse circuit fromr the impulse relay A, (Fig. 2). releases at the end of the stations series of impulses, a circuit to operate relay LP is closed as follows: battery, Winding relay LP, 362, 369, 511, 512, brush 594 (ofir1 normal), 509, 510, 367, 368, to ground at 341 of relay ADV. Rel-ay LP looks in the man-ner previously described. Y,

Thus, it Will be seen that in either case the relay LP is operatedl under control of relay ADV in order to advance the progressl of the call.

The operation of relay LP opens at 315 the holding circuit for relays S`T-1 and SlT-2 which release and relay STF-'1, in releasing', opens at its armature 370 the locking circuit for relays S113' and ST4 which release. The release of relay ST-3 opens at 351 the locking' circuit for the Z and W timii'ig relays which also release, and th-e release of relay ST-4 opens the circuit including the impulser 342 and the relay BB.

The assis-rumentI lam-p 401 (Fig. 4) now lights over the following,` circuit: battery., relay LP, 311, resistance 372, 333, 233, brush 223, 243, 252, 476, lamp 401 to ground at403.l

Display/ng the called number.

The display key DK 2) is depressed, and relays. K and PO operate in series as follows: battery, Winding relay CON (Fig. 4), Winding relay PO, right Winding relay K. eea, 25e, 254, 255, 25e, 400, 257, 216, to ground at 217 of relay SLO. Relay L operates under control of relay PC and locks in series with the peg count register MR, The register MR. operates and registers the call, and short-circuits the relay L which releases. The register MR remains lockedv until the relay PO` releases. The relay K, operated, locks as follows:l battery, winding relay CON, ,Winding relay PO, windings relay K, 4105,. 411, 412, 406, 407, 408, 409, 257, 216, to ground at 217 of relay SLO. The relay K1 operates` over an obvious circuit under control of relay K.

Relays MG and SNR (Fig. 3) operate under control of relay K over the following lVhen relay ADV circuit: battery, winding relay MG, winding relay SNR, 335, 235, brush 225, 245, 248, 413, to ground at armature 414 of relay K.

The home lamps control relay HL, and relay REL, (Fig. 3), operate in parallel over an obvious circuit under control ot relay MG, and relay HL connects ground at 373 to 377, inclusive, to the brushes 501, 561, 571, 581, and 591, respectively, of the numerical register switches Fig. 5. Each lead in each arc associated with each ot the brushes aforesaid, is connected to a lamp such as lamps 550 to 554, inclusive or other suitable number indicating device. Hence, circuits from battery through the proper lamp by way of the brushes are closed to ground at relay HL .displaying before the operator in the manual central otlice MCO (Fig. 4) the number ot the desired line and the proper party code. Relay REL operated, short circuits the resistance 302 and causes lamp 300 of the register circuit to glow brightly as an indication that the call is progressing properly.

The form and type of the number indicating device used is not material to this invention. The device may be in any form, a suitable one being described in Automatic Telephony by Smith and Campbell, second edition, p age 240, and shown therein at page 250, Fig. 217.

Before inserting the plug 423 in the jack 424 of the called line, we will discuss the further setting of various relays, particularly the ringing relays RP and RV (under control ot the register switches) .l

The circuit through the assignment lamp 401 is opened at 403 by the operation ot relay K1, thus extinguishing the lamp.

Relays TR1 and TR2, which are in parallel, now operate over an obvious circuit to ground at 416 of relay K1. Relay TR1 locks by way ot' 249 under control of relay SLO, removes at 258 and 259 the short circuit rom around windings 206 and 207, respectively, of the repeating coil (it will be recalled that windings 206 and 207 were short circuited during the dialing period to prevent distortion of the impulses transmitted to the impulse relay A). Relay TR2 is held operated under control of relay TR1, opens at 236 the impulse circuit controlled by impulse relay A, at 218 the battery feed-er to relay T, and at 213 the operating circuit for relay CI-l. Relay (ll-1 does not release, because a substitute holding circuit was provided by the operation ot relay K1 as follows: battery, stepper 210, 211, winding relay (l-1, 260, 419, 417, 418, 420, 261, 215, 216, to ground at 217 ot rel lay SLO.

'The operation of relay K connected the relay RP to the register circuit by way of 427, 448, and brush 221 -o'f the recorder finder switch, likewise, the operation of relay Kl connected relay RV to the register circuit by Way of 415 and brush 224 of the same switch. Relays RV, RP and PU control the type of signaling current supplied to the called station and the station signalled on a party line will depend upon the operated or normal condition ot' these relays.k

For purposes of illustration, let us assume that party: W is signalled by applying battery of negative polarity superimposed with alternating current to the'ring conductor 421 of the called line 400. M is signalled by applying battery ot negative polarity superimposed with alternating current to the tip conductor 422 of the called line 400. R is signalled by applying battery ot positive polarity superimposed with alternating current to the ring conductor 421 'ot' the called line 400. J is signalled by applying battery of positive polarity superimposed with alternating current to the tip conductor 422 of the called line 400.

To signal the various parties, it will be necessary to operate relays PU, RP and RV according to the following table:

W, RP and RV normal.

M, PU and RV operated RP normal.

R, RP operated PU and RV normal.

J, PU, RP and RV operated.

It the calling station 200 desires to call the party J the digit 5 corresponding to the code letter J would be dialed; similarly for M the digit 6, for R the digit 7 and for W the digit 9.

The stepper 555 (Fig. 5) would rotate and step the brushes 590 to 595, live, six, seven or nine steps to the corresponding terminals of the stations register arcs. For J this would be live steps or terminal 518 of the arc associated with brush 595, for M six steps or terminal 519, tor R seven steps or terminal 520, and `tor W nine steps or terminal 521.

Assuming the stations register is set'or party 1V, then brush 595 will be resting on terminal 521 and no circuit will be closed. Hence, relays RP and RV remain normal.

Assuming, however, that party M is required, then with brush 595 resting on terminal 519, a circuit to operate relay RV (Fig. 2) will be closed as follows: battery, winding relay RV, 262, 425, 415, 426, 263, 264, 265, 244, brush 22a, 23a, ssa, 522, 519, brush 595, 523, 380, to ground at 381 ot relay REL.

Assuming party R is required, then with brush 595 resting on terminal 520, a circuit to operate relay RP (Fig. 4) is closed as tollows: battery, winding relay RP, 427, 448, 449, 251, 241, brush 221, 231, 331, 383, 524, 520, brush 595, 523, 380 to ground at 381 of relay REL.

Assuming party J is required, then with brush 595 resting on terminal 518, a circuit to operate the relay OPV (Fig. 3) will be closed as follows: battery, winding relay orv, 384, 525, 51s, brush 595, 525, 380, to ground at 381 of relay REL. Relay OVP operated, connects ground at 379 to lead 331 to operate relay RP and at 378 to lead 334 to operate relay RV. Relay RP, if operated loclrs over an obvious circuit to ground at 217 of relay SLO. Likewise, relay RV if operated, locks over an obvious circuit to the same ground.

Complet/fag 1571,@ connection.

Vhen the plug' 423 of the trunk (Figs. 3 and 4) is inserted in the jack 424 of the called line 400, relay SL (F ig. 4) operates over the sleeve in series with relay CO to ground. The hol-ding circuit for relay K is opened at 407 and 408 of relay SL and rep lay K releases, in turn releasing relay K1 (Fig. 4) and relays SNR and MG (Fig. 3). The holding circuit for relay CSi-1 is opened at 417 and 418 by the release of relay K1, and relay (l-1 releases releasing relay (1I-2. Relays Cl-1 and (l-2 open the various circuits over brushes 220 to 225, inclusive, previously described, releasing` the recorder and register for service, if required by some other stations trunk.

Vile will delay a discussion of the return to normal of the recorder and register circuits until after the call has been completed to station 400.

Relay SL operates relay R2 in parallel with the disconnect lamp 428 as follows: (path 1) battery, 429, lamp 428, 430, 431 to ground at 432, (path 2) battery, 429, 433, 266, 267, 268, 269, 434, 489, winding relay R2, 490, 491, 479, 493, 492, 431, to ground at 432. The lamp 428 will not glow due to the low resistance winding of relay R2 in parallel with it.

Signaling the called party.

The' pick-up relay PU operates when the interrupter 435 connects battery to lamp 436 for a brief interval before the commencement of the machine ringing cycle. Machine ringing and the function of the pickup relay are so well known in the art that it is not proposed to explain the operation of this portion of the system in any detail.

To ring party lV (relays RP and RV normal) the circuit would be as follows: sig naling current from the ringing machine to 441 and right winding relay TRPG, 443, 444, 445, 270, 271, 272, 273, 450, 451, 452, 453, 454, 455, 421, 456 to ground at ringer 457.

To ring party M (relays PU and RV operated) the circuit would be as follows: signaling current 441, right winding of rela TRPG, 443, 444, 458, 488, 487, 486, 274, 275, 276, 277, 459, 460, 461, 462, 463, 464, 465,

466, tip conductor 422, to ground through the condenser and ringer in series at station M (not shown).

To ring party R (relay RP operated and relay RV normal) the circuitV would be as follows: signaling current 442 and left winding of relay TRPG, 494, 468, 469, 444, 445, 270, 271, 272, 27s, 450, 451, 452, 453, 454, 455, ring conductor 421 to ground through the condenser and ringer in series at station R (not shown).

To ring party J (relays PU, RP and RV operated) the circuit would be as follows: signaling current 442 and left winding of relay TRPG, 494, 468, 469, 444, 458, 488, 487, 456, 274, 275, 275, 277, 459, 45o, 451, 462, 463, 464, 465, 466, tip conductor 422 to ground through the condenser and ringer in series at station l (not shown).

A single party line will be signalled in the same maner as the lV party in a multiparty line.

During the signaling period, ground will be connected to the line conductor which is not connected to the source of signaling current at one of the contacts 278 or 279 of the relay RV. One reason for this is to prevent the false signaling of parties on the opposite side of the line at the moment the :receiverl is removed from the switchhook at the called stati-on. The ground at 278 or 27 9 operates to short circuit the ringers on the opposite side of the line to accomplish this object. Another reason for this is to supply a lground return during signaling on a single party line.

During the signaling period, part of the ringing current flows through one ofthe condensers 470 or 471 and one of the windings 279 or 282 of the repeating coil (Fig. 2) inducing alternating current in one of the associated windings 206 or 207 of the repeating coil, thereby transmitting alternating curr-ent back over the trunk to the calling station 200, which furnishes a tone in the receiver 283 as an audible indication that the ringing current is connected to the called line.

The called station will be signalled and the receiver 467 will be removed from the switchhook. The relay TRPG is designed to be slow to operate so that it will not open its contacts 493 `and 479 during signaling, but the moment the receiver 467 is removed from the switchhook the impedance of the signaling circuit including relay TRPG is reduced so as to allow the relay to operate and separate its armature 479 andback contact 493, thus removing the short circuit from the winding of relay R3 which operates in series with relay R2, short circuiting the latter at 480 and 490 and causing its release. The `effect of this operation is to substitute the relay R3 for the relay R2 previously in parallel with the disconnect lamp lll) si, aso, ase, les, 45a, 45s, 454-, 455, 421, Sta-` tion 400, 422, 466, 465, 464, 463, 462, 461, 472, 473, 281, to ground at 282. The S2 relay now operates under control of relays S1, TR1 and SLO. Relay S2 reverses the direction of the current flowing in the trunk conductors aud the repeater R to operate avcall charging device (not shown) associated with the calling line 200.

The stations 200 and 400 are now connected together and conversation takes place.

Dischargz'rtg the recorder circuit cmd the rcgzstcr s/wztcics.

After the called number was displayed upon the indicator, the ringingcombination set and the plug inserted in the jack of the called line, the recorder circuit and the register switches (Figs. 3 and 5) were no longer required, hence, the SNR and MG relays (Fig. 3) released upon the release of relay K and the Ol-l relay (Fig. 2) and LP relay (Fig. 3) released upon the release of relay K1. The release of the relays SNR MG releases relays HL and REL (Fig. 3). The release of the former extinguishes the display on the indicator before the operator, and of the latter extinguishes lamp 300, and releases relay OPV (if .operate-d).

The releaseof relay Oli-1, released the relay O1-2 (Fig. 2) and relay HLD (Fig. 3) which were in series. The release of relay HLD opens the circuit of relay GRD, but the latter remains operated over leads 385 and 527 to ground at brushes 503, 563,573, 583, and 593, which are off normal. Hence, as long as any one of the register switches are oit normal the relay GRD remains operated, holding the recorder circuitbusy to all other trunks until relay GRD releases as hereinafter described.

The release of relay HLD operates relay RES (Fig. over an obvious circuit controlled by the relay GRD.

Stepper now operates to restore the stations register switch to normal over a circuit as follows: battery, 319, winding relay ADV. 318, 517, 516, stepper 528, 529, 53o, ssc, 387, ses, asa, 531, brush 59a (ofi:l normal) 509, 510, 367 lto ground at 321 of relay HLD.

lVit-h the stations switch in normal position, a circuit similar to the one traced for the station switch, is closed by way of brush 584, and one of the terminals 531 or 508 of the stations register switch arc to' operate the units register stepper' 545.

In like manner .each of the Steppers 535, 525 and 515 operate in sequence to restore their respective register switches to normal. )Vith all the register switches in the normal position relay GRD releases, releasing relay RES and restoring the recording circuit and register switch to normal.

@all/ng party/f disconnects first. lVhen the receiver 283 is replaced on the switchhook 247 at station 200, a circuit including the repeater R (Fig. 2) is opened, causing the repeater to restore to normal and open the holding circuits for the primary line switch PLS,-the secondary line switch SLS and selector S, which also restore to normal.

lVhen the repeater R releases, the circuit including the repeater R and the impulse relayA is opened causing the relay A to release. The circuit through the relay SLO is opened b i the release of relay A releasing relay The release of relay SLO opens at its contact 217 the holding circuits for relays TR1, TR2, S-2, RV and RP, releasing these rela1 s.

' The release of relay TR1 removes the shunt formed by the winding of relay R3 from around the disconnect lamp 428 releasing relay R3 and lighting the lamp 428 as a disconnect signal to the operator in the manual central oflice MOO. When the plug 423 is removed from jack 424, relays S1 and SL release, the disconnect lamp 428 is eX- tinguished and the circuit is restored to normal.

Called party disconnects inst-)Viren the receiver 467 is replaced on the switchhook at station 400, a circuit including relay S1 is opened at the switchhook contacts releasing relay S1 which in turn releases relay S2.

A circuit is now closed to operate relay ST (Fig. 1) as follows: battery, winding relay ST, 100, 284, 285, 286, 287, 484, 485, 474, 475, 476, lamp 401 to ground at 403 of relay K1. The lamp 401 will not light due tothe high resistance of relay ST in series with it.

The operation of relay ST closes an obvious circuit to operate relay OT. The interrupter 103 is now connected to the relay INT by way of 104 and 105. Relay INT operates, connectingground intermittently to lead 108 by -way of 106 and 107.

The timing relays 1V?) and Z3 to )V7 and Z7 operate in the same general manner as the timing relays W and Z to V72, Z2 (Fig. 3) except that relay Z7 does not lock up permanently in the same manner as relay Z2.

Vhen relay Z7 is operated and relay lV7 is normal, a circuit is closed to operate relay PS by way of lead 102 to ground at armature 101 of relay OT.

The relay CA operates over an obviouscircuit including Contact 112 of relay PS. When the timing relays release, relay PS also releases, allowing relay CB to operate in series with relay CA, thus connecting relay CC by Way of lead 111 to the contact 112 of relay PS. The timing relays Z3, V73 to Z7, W77, reoperate, under control of interrupter 103, and relay PS operates in the manner previously described. When relay PS reoperates at the completion of the second cycle of operations of the timingrelays, relay CC operates as follows: battery, relay Ps, 112, 111, 11a. 11i, 115, 11e, winaing relay CC to ground. Relay CC locks under control of relay CB by Way of 116, 117, 118 and 119. The lamp 120 (Fig. 1) located in the switchboard before the operator in the manual central oiiice MCO (Fig. 4) lights over an obvious circuit as an indication to the operator that one of the trunk circuits in her position has been held for an unreasonable length of time after the called party has disconnected.

The lamp 120 is common to all the trunks in the position and in order to ascertain the particular trunk in the position which is effected, the operator depresses the flashing key FK (Fig. 1) thereby shunting the relay ST by tl e resistance 110. The resistance of the parallel combination of the Winding of the relay ST and the resistance 110 is such as to permit the assignment lamp 401 (Fig. 4) to light as an indication that this. trunk is the one which has been held up for an improper length of time.

The operator now removes the plug 423 from the jack 424 and inserts it in a jack associated with the circuitof a supervising operator, who challenges on the trunk to ascertain Whether or not station 200 is still on the line.

[ucompZetcd calls.

Should the station 200 originate a call and operate the dial for one or more digits, but fail for any reason to dial a sufficient number of digits, to set the thousands, hundreds, tens and units register switches (Fig. 5) the call will not progress and the lamp 300 ig. 3) Will remain lighted dimly for an undue length of time. The attendant will observe this and depress the incomplete display key IDK (Fig. y3). This will light the assignment lamp 401 as follows.: battery, key TDK, resistance 372, 333, 233, brush 223, 243, 252, 402, 476, assignment lamp 401, to ground at contact 403 of relay K1. The operator at the manual cent-ralv oiiice MCO (Fig. 4) will operate the display key DK (Fig. 3) operating the relay K in the usual manner. Relays K1, MG,

SNR, REL and HL Will operate in the manner previously described and those digits which have been dialed Will be diskeys J, M, R or vbefore the manual andrequest him to disconnect and originate another call. l

AZZ recorders busy.

If all the recorders (Figs. 3 and 5) are busy at the time the trunk is seized by the repeater R, the (l1-1 and C1-2`relays will not operate.

1When the subscriber at the calling stat-ion 200 starts to dial, the impulse relay A releases, operating-relay MC, as follows: battery, windings relay MC in series, 283, 289, 233, 237, 236, to ground at armature 229 of the impulse relay A. The relay MC locks by Way of 290 and 216 to ground at 217 of relay SLG. Relays TR-1 and TIR-2 operate in parallel' as follows: battery, Windings TR-l and 'TR-2 in parallel, 291, 292, 293, 294, 256, 405, 406,407, 408, 409, 257, 216, ground at 217 of relay SLO. The disconnect lamp 42S (Fig. 4) now lights over a circuit as follows: battery, resistance 429, lamp 428, 430, 477, 478, 295, 296, 297 to ground at 298. The operator at the manual central otlice MCO Will connect the trunk to a supervising operator Who will determine the number of the desired called line.

The proper signaling current will be applied to the line by operating one of the 7V (Fig. 2) which Will operate the relays RP or RV, or both, as the case may be, in the same general manner and with the same general results as in a regular call by way of the recorder and register circuits. After removing the plug 423 of the trunk from the jack associated with the supervising operator the display ley DK is depressed and relays K and Kl operate and lock` as in a regular call.

The plug 423 will then be inserted in the jack of the desired line and the call will progress in the usual Way.

TWhenever `all recorder circuits in the group are busy thc brushes of any idle recorder linder will advance until they rest upon the terminal corresponding to the terminal of all other recorder linder switches. The terminal 242 which is connected to the lead 226 is multipled to the terminal of all other recorder finder switches corresponding to the terminal 242. Lead 2.26 is also multipled to the Contact 390 of the relays GRD associated with all the recording circuits in the group.` As long as the recording circuits are busy all the relays GRD Will be operated and the common lead 226 will be free from ground. )Whenever any recorder circuit becomes idle its relay. GRD will release, connecting ground to terminal 242 by way of lead 226 and contact 390. The relays T individual to the various idle trunks will now operate in parallel over a circuit as follows: battery at relay TR2, 218, winding relay T, 240, brush 220, terminal 242, common lead 226 to ground at 390 of relay GRD. The Various relays T will operate and close the circuit to the various steppers similar to 210 which will operate, open their operating circuit and release, and in so doing step the brushes of their respective switches to the terminals corresponding to terminal 227, thence to the terminal corresponding to terminal 228 in the sam-e manner. In this way the various recorder `finder switches individual to the various trunks vin the trunk group are at all times resting upon a preselected idle recorder circuit if an idle circuit is available or if all recorder circuits are busy are resting upon a particular terminal of the switch arc, where they will remain until a recorder circuit becomes idle when they will again proceed to preselect the idle recorder circuit.

It should be understood that the number of line switches may be increased or reduced as desired without departing from the spirit of the invention.

It should also be understood that the number of selector switches introduced between the calling subscriber and the trunk circuit may be varied as desired without in any way departing from the .spirit of the invention.

It should also be understood that the trunk repeater may be entirely omitted or additional trunk repeaters inserted as required without in any way `departing from the spirit of the invention.

What is claimed is:

l. A telephone system comprising a calling line, an impulse sender, an impulse relay, a circuit including the calling line and the impulse relay controlled by the impulse sender, a plurality of selector switches operable in sequence, a slow relay, an impulse circuit including one ofthe selector switches and the slow relay controlled by the impulse relay for setting the selector switch and operating the slow relay, means controlled by the joint action of theslow relay and of each selector switch in sequence excepting the last, for substituting the next succeeding selector switch in the sequence for the prior selector switch at the end of the corresponding impulse train until all the required selector switches in the train have been properly set, means for indicating the progress of a call, manually controlled means for releasing the selector switches, a called line, manually controlled means for linking the calling and called lines together, and signaling means for summoning the called line.

2. A signaling system comprising an impuiser, a train of timing relays, a circuit including the impulser and theelays 1n succession whereby the relays measure oif substantially uniform time intervals, means for locking the last relay in the train thereby permitting the other timing relays to continue to measure ed additional time intervals until all the relays in the train are again operated in succession, a timed device, and a circuit controlled by one or more of the timing relays in combination for functioning the timed device.

8. In a telephone system, an operator-s position, a plurality of lines terminating atsaid position, the numbers of which include a variable number of digits, a register set comprising sufficient registers to register the number of a called one of said lines containing the maximum number of digits, means controlled by said registers for indicating lo the operator any registered number, and a train of counting relays operable todelay the operation of said means until suiiicient time has elapsed to enable the maximum number of digits in any number to be regisn tered.

el. In a telephone system, an operators position, a plurality of lines terminating at said position the numbers of which include a variable number of digits, a register set comprising sufficient registers to register the number of a. called one of said lines containing the maximum number of digits. means for setting said registers in succession, means controlled by said registers for indicating to the operator any registered number. a train of counting relays operable to delay' the operation of said last means until sufficient time has elapsed to enable the maximum number of digits in any number to be reg' stered, and means operable following the setting of an intermediate one of said registers for initiating the operation of said relays.

5. In a telephone system, an operators position, a plurality of lines terminating at said position, the numbers of which include a variable number of digits, a register set comprising suflicient registers to register the number of a called one of said lines containing the maximum number of digits, means for setting said registers in succession, means controlled by said registers for indicating to the operator any registered number, means operative following the setting of the last one of said registers for controlling said indicating means, a train of counting relays operable to Ldelay the operation of said last means until suiticient time has elapsed to enable the maximum number of digits in any number to be registered, and means operable following the setting of an `intermediate one of said registers for initiating the operation of said relays. Y

6. In a telephone system, an operators position, a plurality of lines terminating at said position, the numbers of which include a variabley number of digits, a register set comprising suiiici-ent registers to register the number or' a called one of said lines containing the maximum number of digits, means controlled by said registers for indicating to the operator any registered number, a signal for apprising the operator when a number is fully registered, a timing mechanism operable to delay the operation ot said signal until suliicient time has elapsed to enable the maximum number of digits in any number to be registered, and operator controlled means for operating said indicating means.

7. In a telephone system, an operators position, a plurality of lines terminating` at said position, the numbers oi' which include a variable number of digits, a register set comprising sutlicient registers -to register the numb-er of a called one of said lines containing the maximum number of digits, means controlled by said registers for indicating to the operator any registered number, a lamp for apprising the operator when a number is fully registered, a train of counting relays operable to delay the lighting of said lamp until suiiicient time has elapsed to enable the maximum number of digits in any number to be registered, and operator controlled means for operating said indicating means.

8. In a telephone system, an operators position, a plurality of lines terminating at said position, the numbers of which include a variable number of digits, a register set comprising sulieient registers to register the number of a called one of said lines containing the. maximum number of digits, means controlled by said registers for indicatingto the operator any registered number, and a timing device comprising a train of counting relays and an interrupter operable to delay the operation of said means until suiiicient time has elapsed to enable the maximum number of digits in any number to be registered.

9. In a telephone system, an operators position, a plurality of lines terminating at said position, the numbers of Which include a variable number ot' digits, a register set comprising sufficient registers to register the number ot a called one et' said lines containing the maximum number ot digits, means controlled by said registers for indicating to the operator any registered number, and a timing device comprising a train of counting relays and an interrupter operable to delay the operation ot said means until suiiicient time has elapsed to enable the maximum number ot digits in any number to be registered, said relays being con-v nected in circuits such that said relays are operated by said interrupter in succession and repeatedly.

l0. In a telephone system, a timing device comprising an impulser, a train of timing relays, a circuit including said impulser and the relays in succession whereby the relays operate through a plurality of cycles to measure oit substantially uniform time intervals, a. signaling device and means operated by said last relay in the train at the end ot' said plurality of cycles for operating said signaling device.

ll. In a telephone system, an operators position, a plurality of lines terminating at said position, a calling line, means for establishing a .connection with a desired one of said called lines including a plug-ended trunk circuit at said operatorls position, a signaling device at said position, a timing device operable following the restoration of the. called subscribers receiver'to its switchhook, and means operable by said timing device to operate said signaling device if the calling subscriber delays in hanging up his receiver.

l2. In a telephone system, an operators position, a plurality of lines terminating at said position, a register set comprising sufficient registers to register the number ot a called one of said lines, means for setting said registers in succession, a progress lamp, and means for lighting said lamp il an undue delay occurs in the setting of said registers.

In witness whereof, I hereunto subscribe my name this 21 day of November, A. D.

ALBERT C. POWELL. 

